By golly your right mikekeswick!!! A company called Rockler sells a linseed oil and pine resin varnish. I'm always looking for authentic formulas for varnishes, thanks.
adb, Sorry for my misstatement, I was only trying to show that even in the late seventeen hundreds, men like Franklin were well aware of the English Warbow and its capabilities, and by inference, the associated crafts such as varnish making would also have been passed down through families engaged in that craft, and or guilds of the same nature.
Robby